In the past, a MEMS switch for transmitting a high frequency signal which employs the static actuator is well known. Such the MEMS switch is disclosed in Japanese patent publication No. 3852224B.
The MEMS switch disclosed in the Japanese patent publication No. 3852224B comprises a substrate, a movable plate, a pair of signal wires, and a static actuator. The substrate is made of a glass. The movable plate comprises a movable contact. The substrate is provided at its upper surface with a strip. The strip has flexibility. The movable plate is supported by the substrate via the strip such that the movable plate is movable in a thickness direction of the substrate. Consequently, the movable contact is supported by the movable plate such that the movable contact is movable in the thickness direction of the substrate. A pair of the signal wires is disposed on the upper surface of the substrate. The signal wires are provided with fixed contacts, respectively. The fixed contacts are configured to come into contact with the movable contact when the movable contact is displaced in the thickness direction of the substrate. The static actuator is provided for displacing the movable plate such that the movable contacts moves toward the fixed contacts. The static actuator comprises a movable electrode and a fixed electrode. The movable electrode is disposed on the movable plate. The fixed electrode is disposed on the substrate to be located in an opposed relation to the movable electrode. The movable electrode is configured to come into contact with the fixed electrode when the voltage is applied between the movable electrode and the fixed electrode. In addition, the fixed electrode is provided at its upper surface with an electrically insulation film. The electrically insulation film is provided for prevention of the sticking of the movable electrode to the fixed electrode. The movable plate is made of silicon.
Furthermore, in the past, a MEMS switch comprising a static actuator and a piezoelectric actuator is also well known. The MEMS switch is used for transmitting the high frequency signal. The MEMS switch is configured to be operated by electrical power which is lower than electrical power for operation of the MEMS switch comprising only the static actuator. Such a MEMS switch is configured to allow the movable contact to move toward and away from the fixed contacts of a pair of the signal wires by means of the static actuator and the piezoelectric actuator. Such a MEMS switch is disclosed in Japanese patent application publication No. 2008-27812A.
The MEMS switch disclosed in the Japanese patent application publication No. 2008-27812A comprises a substrate, a pair of signal wires, and a flexible layer. The substrate is made of glass. A pair of the signal wires is disposed on the upper surface of the substrate. A pair of the signal wires is provided with fixed contacts. The flexible layer is provided with a first end and a second end. The first end of the flexible layer is fixed on the upper surface of the substrate. The second end of the flexible layer is provided with a movable contact. The movable contacts are configured to come into contact with the fixed contacts. The flexible layer is realized by a bimorph type piezoelectric actuator. The bimorph type piezoelectric actuator comprises a lower electrode, a lower piezoelectric layer, an intermediate electrode, an upper piezoelectric layer, and an upper electrode. The lower piezoelectric layer is made of AlN. The lower piezoelectric layer is disposed on the upper surface of the lower electrode. The intermediate electrode is disposed on the upper surface of the lower piezoelectric layer. The upper piezoelectric layer is made of AlN. The upper piezoelectric layer is disposed on the upper surface of the intermediate electrode. The upper electrode is disposed on the upper surface of the upper piezoelectric layer. The tip of the lower electrode also acts as the movable electrode of the static actuator. The fixed contact also acts as the fixed electrode of the static actuator.